<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>css3盒子模型</title>
    <style>
        div{
            width: 200px;
            height: 200px;
            background-color: lightpink;
            border: 20px solid blue;
            padding: 15px;
            /* 以前默认盒子，会根据内外边框撑大盒子 */
            box-sizing: content-box;
        }
        p{
            width: 200px;
            height: 200px;
            background-color: lightpink;
            border: 20px solid blue;
            padding: 15px;
            /* 不会撑大盒子 */
            box-sizing: border-box;
        }
    </style>
</head>
<body>
    <div>小花</div>
    <p>非洲菊</p>
</body>
</html>